yes. you may use it for bar.
it's up to you what do you want to use as inventory units for specific item. then fractions of these units will be deducted from stock with each sale.

normally you add items to stock by using Purchasing - Receive Vouchers. in recent version we also added possibility to add to stock directly on menu Configuration - Items window. but it's better to use Receive vouchers for opening stock quantities. because with receive voucher you may set initial quantity and cost.